Holding back the rising tide

Luke Jackson from the Institute for New Economic Thinking at the Oxford Martin School explains how achieving the Paris Agreement could help to slow sea-level rises.

Achieving the aim of the Paris Agreement, to hold the rise in global average temperatures to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, by the end of this century could dramatically reduce potential sea-level rise compared to projections based upon business-as-usual scenarios.

A lot of research on sea-level change had previously focused upon high future Global Warming. Since the Paris Agreement was signed in late 2015, there has been a switch in focus to think carefully about how the climate (including sea level change) will respond if we succeed in achieving Paris’s aims.

Future sea-level rise has the potential to affect millions of people and billions of dollars’ worth of infrastructure world-wide by increasing the vulnerability of coastlines to flooding from tides, wind-driven waves and storm surges.

In our own study published this month - 21st century sea-level rise in line with the Paris accord - we apply a novel method to project future sea-level rise at a global and a regional level for the two temperature levels stated in the Paris Agreement.

The new research shows that achieving a 1.5 °C or 2 °C temperature rise by 2100 could result in a global sea-level rise of 44 cm and 50 cm respectively. This is in contrast to a rise of 84 cm for a business-as-usual scenario if temperature rises around 4 °C by 2100. The difference between achieving Paris and a business-as-usual scenario is even more marked when comparing low-chance (1-in-20), high impact projections. In this case, the global projections are 67 cm versus 180 cm for 1.5 °C and business-as-usual respectively, a difference of more than 1 metre.

Differences of this size are significant for decision makers regarding Climate Change mitigation (achieving the Paris Agreement will require rapid, deep emissions reductions) and coastal adaptation strategies.

The full paper, ‘21st Century Sea-Level Rise in Line with the Paris Accord’, by Luke Jackson, Aslak Grinsted and Svetlana Jevrejeva, can be read in Earth’s Future.